The Cityquartier DomAquarée in Berlin is one of the most fantastic engineering feats you will run across. The AquaDom is a “multi-use development, including a world-renowned four star hotel, retail, recreation, living and office space” that just happens to have the world’s largest cylinder aquarium running up the center of the hotel complex. The aquarium is over 52 feet deep and 36 feet in diameter and contains over 2,000 fish. The AquaDom website has some amazing photos of this complex and detailed planning and construction information that is very interesting. I would love to visit this complex and ride the glass elevator that runs up the center of the aquarium.